316 Illinois State Laboratory of Natural History. 



the imago. From a few of these, parasites bad evidently 

 escaped, but in most cases there was nothing in the external 

 appearance of the cocoon to explain the failure of its develop- 

 ment. Returning to this region June 3d of the following year, 

 we learned from A. J. Ayers, Esq., of Villa Ridge, that a suf- 

 ficient number of larvae hatched that spring to do considerable 

 damage, but that when they were a little over one half an inch 

 long they died and dried upon the leaves, sometimes whole 

 colonies being found dead together. Occasional examples of 

 larvae in this condition could even then be found on the apple- 

 trees. A few apparently healthy examples were collected at 

 this date and brought to the Laboratory at Normal. These 

 were carefully fed and attended, with the expectation of obtain- 

 ing the imago, but all died, without exception, with symptoms 

 precisely resembling those of the year before, as they then 

 came under my observation. 



The first of these larvae was seen to be sick on the 27th 

 June, ejecting from the mouth and vent a fluid which contained 

 great numbers of oval corpuscles, not unlike those character- 

 izing pebrine, but varying appreciably in size and shape. 

 Examples were found in process of sub division, or even, in 

 occasional instances, short strings of three not wholly separated; 

 and other examples occurred where a spherical lobe was borne 

 upon the end of an oval cell, as if the latter were budding end- 

 wise. All these appearances were inconsistent with the hypoth- 

 esis of the presence of pebrine, the characteristic "corpuscles" 

 of which develop by internal segmentation of spherical masses 

 (Sporozoa) and are never connected in doubles nor multiply by 

 fission. Dissections of these larvae afforded evidence that they 

 were attacked by muscardine. In specimens which had lain 

 some time it was not difficult to identify a scanty mycelium in 

 the body, although, owing probably to the dry and warm 

 weather at this season, there was no external development of 

 the fungus either in the form of threads or spores. These 

 larvae continued to die until July 5, at which time the last 

 perished. 



The individual cells found in the blood varied from 2 ^ to 

 3.5 p, and in length from 3.5 ^ to 5 p>. They differed also in 

 shape, some being a rather broad symmetrical oval, and others 



